This relates to graphics processing.
It is common to use a sort-middle architecture for a mobile device. As in any graphics application, it is important to reduce power usage.
Geometry processing may be made parallel by assigning to each processor a subset of the primitives in a scene. Rasterization may be made parallel by assigning to each processor some portion of the necessary pixel calculations. Rendering involves calculating the effect of each primitive on each pixel. A primitive can fall anywhere on or off the actual viewing screen. Rendering sorts the primitives to the screen. The sort can take place during geometry processing in what is called sort-first, between geometry processing and rasterization, called sort-middle, or during rasterization called sort-last. Sort-first means redistributing raw primitives before their screen-space parameters are known, sort-middle means redistributing screen-space primitives, and sort-last means redistributing pixels, samples, or pixel fragments.